Knowledge of depth-resolved snow density and its spatial distribution is essential for many scientific and operational applications. However, direct manual snow density observations are typically time-consuming and potentially incomplete, while spaceborne and airborne methods are still in development. In this contribution, we introduce a newly developed laser-based method for estimating snow density. We present details on the measurement concept and lab experiments carried out to build a first prototype. The Snow Laser Drill (SLD) method involves melting a long narrow hole into the snow with a high-energy melting laser. The melting process is tracked with a laser rangefinder. Based on the melting rate, the snow density can be deter-mined using a thermal model. The two lasers are set in a protective housing and (dichromatic) mirrors are used to collinearly align both beams. During the lab tests, different output power settings and snow densities were trailed. Results show that the SLD can measure depth-resolved snow densities in the millimetre-range. At constant snow density there is a linear relationship between laser power and melting rate; at constant laser power, an indirectly proportional relationship between melting speed and snow density could be shown. The lab experiments showed that this holds true for increasing melt depths as the lasers penetrate the snowpack. It was shown that the average density of a snow sample can be determined with an RMSE of <8.55%. The lab experiments served as a basis for the development of a prototype SLD instrument, which was subsequently field-tested (see part 2 of this contribution). Keywords: Snow density, Laser drilling, Laser range finder, Lab experiments
